Remove alpha badging from terraform state admininistration

Terraform state administration has been in gitlab since 12.10, and
enabled on GitLab.com since April of 2020. I suggest we remove our
alpha badging of this functionality.

doc/administration/terraform_state.md

@@ -4,7 +4,7 @@ group: Configure
 info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
 ---
 
-# Terraform state administration (alpha) **(FREE)**
+# Terraform state administration **(FREE)**
 
 > [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/2673) in GitLab 12.10.